Improve parseInt.

Review URL: http://codereview.chromium.org/6546055

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6888 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/v8natives.js

@@ -92,7 +92,7 @@ function GlobalIsFinite(number) {
 
 // ECMA-262 - 15.1.2.2
 function GlobalParseInt(string, radix) {
-  if (IS_UNDEFINED(radix)) {
+  if (IS_UNDEFINED(radix) || radix === 10 || radix === 0) {
     // Some people use parseInt instead of Math.floor.  This
     // optimization makes parseInt on a Smi 12 times faster (60ns
     // vs 800ns).  The following optimization makes parseInt on a
@@ -105,7 +105,7 @@ function GlobalParseInt(string, radix) {
       // Truncate number.
       return string | 0;
     }
-    radix = 0;
+    if (IS_UNDEFINED(radix)) radix = 0;
   } else {
     radix = TO_INT32(radix);
     if (!(radix == 0 || (2 <= radix && radix <= 36)))